356139bd02
This adds support for generating Chrome-tracing .json profile traces in the LLD COFF driver. Also add the necessary time scopes, so that the profile trace shows in great detail which tasks are executed. As an example, this is what we see when linking a Unreal Engine executable: 
74 lines
2.4 KiB
C++
74 lines
2.4 KiB
C++
//===- MarkLive.cpp -------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "COFFLinkerContext.h"
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#include "Chunks.h"
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#include "Symbols.h"
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#include "lld/Common/Timer.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Support/TimeProfiler.h"
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#include <vector>
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namespace lld::coff {
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// Set live bit on for each reachable chunk. Unmarked (unreachable)
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// COMDAT chunks will be ignored by Writer, so they will be excluded
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// from the final output.
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void markLive(COFFLinkerContext &ctx) {
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llvm::TimeTraceScope timeScope("Mark live");
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ScopedTimer t(ctx.gcTimer);
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// We build up a worklist of sections which have been marked as live. We only
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// push into the worklist when we discover an unmarked section, and we mark
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// as we push, so sections never appear twice in the list.
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SmallVector<SectionChunk *, 256> worklist;
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// COMDAT section chunks are dead by default. Add non-COMDAT chunks. Do not
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// traverse DWARF sections. They are live, but they should not keep other
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// sections alive.
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for (Chunk *c : ctx.symtab.getChunks())
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if (auto *sc = dyn_cast<SectionChunk>(c))
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if (sc->live && !sc->isDWARF())
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worklist.push_back(sc);
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auto enqueue = [&](SectionChunk *c) {
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if (c->live)
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return;
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c->live = true;
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worklist.push_back(c);
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};
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auto addSym = [&](Symbol *b) {
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if (auto *sym = dyn_cast<DefinedRegular>(b))
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enqueue(sym->getChunk());
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else if (auto *sym = dyn_cast<DefinedImportData>(b))
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sym->file->live = true;
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else if (auto *sym = dyn_cast<DefinedImportThunk>(b))
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sym->wrappedSym->file->live = sym->wrappedSym->file->thunkLive = true;
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};
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// Add GC root chunks.
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for (Symbol *b : ctx.config.gcroot)
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addSym(b);
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while (!worklist.empty()) {
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SectionChunk *sc = worklist.pop_back_val();
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assert(sc->live && "We mark as live when pushing onto the worklist!");
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// Mark all symbols listed in the relocation table for this section.
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for (Symbol *b : sc->symbols())
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if (b)
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addSym(b);
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// Mark associative sections if any.
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for (SectionChunk &c : sc->children())
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enqueue(&c);
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}
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}
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}
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